Today uniform product code (UPC) labels are on practically every product produced in the world. Optical barcodes have become so widely accepted because of their low production costs, device complexity, and high durability. These same properties which caused their success now limit their usefulness in commercial applications. The simple design has low production costs, but is severely limited in the amount of data it can represent. The design also allows for simple and cheap detection through optical reading systems. However, optical reading systems require a direct, unobstructed path for light to be emitted onto the barcode and then reflected back to the sensor. This unobstructed (i.e., “line-of-sight”) property of optical read barcodes limits their usefulness. For example, to conduct inventory management, objects must be placed in a specific physical location for their identification information to be read.
To combat the “line-of-sight” problem posed by traditional barcodes, radio-frequency identification solutions have been developed. Radio-Frequency Identification (RFID) tags store and transmit identification information that is similar to the information stored in barcodes. A RFID system consists of an interrogation device that broadcasts a radio signal and a RFID tag which receives said radio signal. With a passive RFID tag, the radio signal power itself is used to power-up a small microchip within the tag, which then transmits its unique identification code back to the interrogation device. The radio waves used to interrogate RFID tags for can pass through many materials, therefore solving the “line-of-sight” issue present in optically read barcodes.
RFID technology does, however, have its own problems. RFID tags can be divided into two major categories: active and passive. Active RFID tags contain their own power source which increases the distance in which it can provide identification information. Problems with this type of tag include cost of production due to the complexity of such a device as well as maintenance issues, physical size and weight constraints, and power consumption. Passive tags overcome cost and complexity issues, but in turn have greatly restricted operability and flexibility. Because a microchip is embedded in an RFID tag, along with radio frequency receivers, front ends, and transmitters, the device complexity and associated cost is much higher than that of optical barcodes.
Because of economic issues industry has been tentative in its adoption of RFID. Wal-Mart Corporation recently rolled out an initiative to have all of their suppliers utilize RFID tagging to aid in their inventory management and supply chain. While this program has benefits, it raises a new problem of data redundancy. Not only will each product now have barcode identification information on it, but it will also have RFID Identification. The use of two identification methods for different purposes is costly and unneeded. Another problem with RFID technology is the separation between an object and its identification information. An object is not directly identifiable as it was when a barcode was embedded directly on the object itself. A tag is affixed to the object, therefore causing all relevant data to be associated with not the object itself, but with a tag on the object. If a tag becomes separated from the object the identity of that object is lost.
One example of the problems associated with data separation caused by RFID technology can be seen in the field of livestock tracking. Since the advent of RFID solutions; the agriculture industry has been attempting to utilize this technology for means of animal identification in the form of a RFID tag affixed to an ear tag placed on the animal. (See U.S. Animal Identification Plan—National Identification Development Team, available on the Internet at the U.S. AIP website information page, hereby incorporated by reference in its entirety.) Studies have shown that approximately 10% of ear tags become separated from the animal throughout its life cycle either by accidental separation, or through human removal. If data relative to an animal is associated with a RFID tag, and the tag becomes separated from the animal all data associated with that animal is also lost. Thus, with RFID technology, information is related not to the object itself, but to a tag which is then associated with the object. This three party identification solution is more complex than a direct identification solution, and is therefore less reliable and less permanent.
One solution to all the aforementioned problems with the above identification technologies is proposed in European Patent No. EP1065623A26 to J. F. P. Marchand, titled “Microwave Readable Barcode” (the EP '623 Patent”), which is hereby incorporated by reference in its entirety. The EP '623 Patent describes a microwave readable barcode that consists of conductive bars made from a conductive ink or conductive foil. Barcode information can be encoded using conductive bars of different lengths, different angles, or different positions. When the device is illuminated by a microwave signal, the encoded information can be read through the attenuation, or non-attenuation, of the signal by the conductive bars, and/or the scattering, or the non-scattering, of the microwave signal by the bars. A complete microwave readable barcode system includes conductive barcodes, a transmitter that radiates a microwave signal onto the barcode, and a detector that senses the microwave signal reflected from the conductive bars. Barcode systems can use multiple microwave signals that differ in one or more respects, such as polarization or wavelength.
While the approach disclosed in the EP '623 Patent solves two problems (the “line-of-sight” readability restrictions associated with optical barcode systems, and the data separation problem associated with RFID technology), the disclosed microwave readable barcodes have limitations and problems. The complexity of a device consisting of either conductive bars of conductive foil causes economic hurdles in the production of the precursor material and in the fabrication of the conductive barcode. Therefore, embedding of a conductive barcode in an object is difficult and costly. The oxidation/corrosion processes limit the reliability of the conductive barcode. High cost of biocompatible metals makes conductive barcodes non-feasible for animal labeling. Also, it is impossible to make an invisible conductive barcode.
Missing from the art is a barcode system that has increased commercial application with increased data representation, and overcomes the problems of data separation, “line-of-sight” issues, and production problems. The present invention can satisfy one or more of these and other needs.